I own a 280 E class 1994 old square shape headlamps W124 engine. It has done 81000 miles and just been serviced by local MB dealer.
At around 77000 miles it developed a "hunting" problem with a tickover speed varying from 800 up to 1800rpm when in neutral when put into drive it settles down to a tickover of around 1000 rpm. Under normal driving conditions the car runs very well.
The car has a Signature warranty.
I asked the dealer to check out this problem
Their initial response was to locate an engine management system black box and substitute it...........this did not cure the problem.
They then fitted a substitute throttle Box system........again this failed to cure the problem . The fitter seems completely at a loss
as to the cause.
Any ideas?

A new head gasket was fitted at around 75000 together with water pump

tom hayes

Over here we call this an idle "surging" problem...

...whereas, the idle speed seems to fluctuate in some cyclical fashion when stopped.

I have been trying to sove this problem with my W124 for years, and just learned to live with it hoping that one day I will find the solution.

But most here claim that a vacuum leak will most likely be the problem. Check all vacuum hoses, replace those that are brittle, and look for any that have come loose from the fittings.

Also a bad MAS (Mass air sensor) could contribute to the problem. This is the cylindrical unit that resides between the air cleaner housing and the main intake.

__________________
2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car

Tom,

Did you ever find the solution to this problem? Please let me know.

THanks,

Matt
1994 E320

Had a similar problem on a volvo. On a cold start in the morning, the engine would rev to about 1300 rpm then fall to 500 and do this for about 30 seconds. Thereafter it settled down to a smooth 750 rpm. I cleaned the idle air control valve and solved the problem.

regards,
Mark

Good suggestions, but 2 problems with it: I don't think I have an idle control valve; and it doesn't settle down. It stays high. I posted elsewhere on this board about my problem, but Tom Hayes seems to have had my exact same problem, and with essentially the same car. I was hoping to see if he ever fixed it, and if so, how.

Anyone else with insight or knowledge, please share!!

Thanks,

Matt

1994 E320 159k

Does anyone know Tom Hayes? Anyway I can get into contact with him about his problem? It appears that this was his one and only post, and he hasn't been back since. Anyone? Or anyone else with a similar problem?

Thanks,

Matt

I located Tom. He said that his intake manifold was cracked and that it had to be replaced; basically the intake manifold developed a leak. I'll update when my car is fixed.

Thanks,

Matt